1. Field of the Invention
The present invention relates to a method and a device for associating or assigning an electronic wheel unit, which is assigned to a wheel of a vehicle and is for ascertaining at least one characteristic parameter of the assigned wheel, with a side of the vehicle.
Such a method and such a device are known in the context of monitoring tire pressures of wheels of the vehicle. The air pressure of such a wheel is subject to changes during the vehicle operation, and the changes can be detrimental to the driving characteristics of the vehicle. Modern vehicles, in particular motor vehicles, therefore include facilities for checking the tire pressures automatically. If the current tire pressures exhibit critical values, this can be indicated to the driver of the vehicle.
For the purpose of establishing the tire pressures, the wheels of the vehicle are assigned electronic wheel units including inter alia sensors by means of which the air pressures can be determined. The data relating to the determined air pressures and further data which is ascertained by the wheel units are transferred, in particular by means of a wireless communication entity, to a central control unit of the vehicle for the purpose of further analysis. In order to enable the control unit to assign the data transferred from the wheel units to correct wheel positions of the wheels on the vehicle, it must know how the wheel units are assigned to the wheels. This is problematic in that the assignment of wheel units and wheels can change as a result of swapping wheels over or installing a spare wheel.
In order to assign such a wheel unit to a side of the vehicle, i.e. in particular to a left-hand or right-hand longitudinal side of the vehicle, the direction of rotation of a wheel can be determined by means of a sensor. In conjunction with an assignment of the wheel unit to an axle of the vehicle, it is possible to carry out an assignment of the wheel unit to a specific wheel position on the vehicle. The assignment of the wheel unit to the axle can be done e.g. by analyzing a signal intensity of a signal which is utilized for wirelessly transferring the data from the wheel unit to the central control unit. The wheel units are usually mounted in the same orientation on a wheel. Because two wheels, and hence the wheel units which are assigned to the wheels, are attached in a mirrored manner at opposing ends of a shared axle, and hence on two sides of the vehicle, the sensors report different directions of rotation when the vehicle is moving. The sensor on the left-hand side of the vehicle normally detects a forward rotation, and that on the right-hand side a backward rotation. If these detections of the directions of rotation are combined with data relating to the actual travel direction of the vehicle, i.e. whether the vehicle is traveling forwards or backwards, it is possible to perform an assignment of a wheel unit to the side of the vehicle.
If the wheel units are implemented as independent components, it can be ensured that they are mounted in the same orientation on wheels. However, if it is attempted to integrate the electronic wheel units in tires of wheels, these featuring e.g. a combination of tires and rims, it is not possible to ensure an identical orientation of the wheel units which are integrated in the tires. It cannot necessarily be guaranteed that the normally symmetrical tires, and hence the wheel units, are mounted in the same orientation on the rims.